Actually I do have good confidence in LP. As mentioned, it is just too easy to slip up, and not worth the risk. Better to play it safe, as she is doing.
Just look at how AF takes a "tumor response of up to 28%" and gives it a negative spin. And has given a negative spin to so many other things said in the past that were positive things in the context they were stated, but taken out of context.
Despite LP being blinded, she might have a "sense" of what might be going on, or even just believed to have a sense. As mentioned: a facial expression, a wink, a cough etc could put this expensive trial (and investor money etc) at risk. Not worth it. In a live conversation about DCVax-L, she might be tempted to say that she "is encouraged" about where things are and perhaps that would already be saying too much.